Rock drill

ABSTRACT

A rock drill actuated solely by a liquid medium under pressure comprises a hydraulic motor for rotating the drill steel and another hydraulic motor for applying axial blows to drill; said motors are hydraulically connected in series, with a valve regulator inserted in the supply circuit upstream of the rotational motor. The striker motor is supplied with liquid both from the outlet of the rotational motor and from an additional source of fluid under a pressure equal to the outlet pressure of said rotational motor, a pressure-adding valve being mounted as a buffer valve between the liquid inlets of the two motors.

United States Patent [191 Montabert ROCK DRILL [22] Filed: Feb. 25, 1972 [21] Appl. No.: 229,311

[30] Foreign Application Priority Data Mar. 18, 1971 France ..71.l0059 [52] U.S. Cl. 173/106, 173/12 [51] Int. Cl. B25d [58] Field of Search 173/12, 15, 50, 51, 105, 173/104, 106, 107, 168, 169

[56] References Cited UNITED STATES PATENTS 1,146,870 7/1915 Haeseler 173/106 1,372,914 3/1921 Smith 173/106 X 1,436,638 11/1922 Bayles 173/106 X 3,406,763 10/1968 Worman 173/107 X FOREIGN PATENTS OR APPLICATIONS 1,056,946 2/1967 Great Britain 175/106 [451 July 9, 1974 Primary Examiner-Werner 1-1. Schroeder Attorney, Agent, or Firm1(arl F. Ross; Herbert Dubno [5 7] ABSTRACT A rock drill actuated solely by a liquid medium under valve being mounted as a buffer valve between the liquid inlets of the two motors.

3 Claims, 2 Drawing Figures ROCK DRILL FIELD OF THE INVENTION The present invention relates to rock drills, ie to hammer drills or percussion hammers adapted to drill holes in hard materials such as rock and concrete and operating by percussion.

DESCRIPTION OF THE PRIOR ART As a rule, tools of this type have been pneumatic driven and were attended by a number of inconveniences rather difficult to overcome, notably the intense noise and the production of air pollution by release of atomized lubricating oil in an aerosol with the exhaust gas; the inconveniences are multiplied when these tools are used for underground drilling operations. Moreover, the efficiency vs. power expenditure is relatively poor.

To avoid these inconveniences, it has been proposed to drive rock drills not with a gaseous fluid under pressure (air) but with a liquid under pressure (oil). In a prior U.S. Pat. No. 3,41 1,5 92 the present Applicant has disclosed an apparatus wherein the percussion is controlled through hydraulic means.

This system actually solved the problem of applying successive blows to the tool of well-point or drill-steel type. However, the problem of tool rotation remained. In fact, the operation of a rock drill requires the combination of two quite different mechanical actions, since the holes to be formed are obtained by applying a rapid succession of blows to the tool while rotating same around its axis.

This tool rotation may be obtained either mechanically, for example by using a nut and ratchet system or a helical ramp system, or hydraulically by using a gear, vane or piston-type hydraulic motor.

In order to be satisfactory, the rock drill operation should be characterized by a complete mutual dependency of these two actions. In fact, rock drilling operations are carried out in very different rock formations, frequently of a heterogeneous nature, and the optimum power rating to be used in each device varies considerably during the drilling.

If a sound rock layer is being drilled, the resistant torque encountered by the rotating drill is low and the maximum percussion power must be applied.

If on the contrary the rock is heterogeneous with inclusions of materials having very different hardness values and such as quartz, clay, the resistant torque varies considerably, e.g. to 10 or 20 times the resistance encountered in homogeneous rock. Under these conditions, the percussion force must be reduced during high torque peaks in order not to torque component which ends up in jamming the drill steel into the heterogeneous material. These frequent changes in the percussion power as a function of the rotational torque should of course take place almost instantaneously in order to provide the best possible conditions of operation.

SUMMARY OF THE INVENTION It is the essential object of this invention to achieve this result automatically and immediately. To this end, the present invention provides a rock drill or like percussion tool or hammer controlled completely by means of liquid under pressure, wherein the hydraulic motor performing the drill steel rotation and the hydraulic motor applying the blows thereto are mounted in series in a common hydraulic circuit comprising, upstream of these two motors, a regulator capable of maintaining at a constant value the pressure of the fluid supplied to both motors.

In this disclosure the term motor is used to designate not only a gear motor, vane motor or piston motor producing the drill steel rotation, but also the driven assembly provided for reciprocating the striker piston along a rectilinear path as required for applying successive rapid blows to said drill steel.

BRIEF DESCRIPTION OF THE DRAWING In the drawing: FIGS. 1 and 2 are diagrammatic sectional views of two embodiments.

SPECIFIC DESCRIPTION In both embodiments the reference numerals designate: 1, the striker unit; 2, the chuck carrying the drill steel 3; and 4 the hydraulic motor comprising a shaft 5 driving the chuck 2 through reduction gears 6.

Also in both embodiments the reference symbol HPl designates the pressure of the liquid fluid at the inlet end of motor 4, and HP2 the fluid pressure at the exhaust or outlet of this motor.

Finally, in both cases, and this is the essential object of this invention, the hydraulic motor 4 and the driven unit or striker 1 are mounted in series in a common hydraulic circuit, whereby the pressure at the inlet of the striker unit 1 is equal to the exhaust pressure of motor 4, i.e., HP2.

Considering the embodiment illustrated in FIG. 1, a pressure regulating valve 7 is inserted in the hydraulic circuit upstream of motor 4. The function of this valve is to keep at a constant value the pressure HPl, i.e. the pressure at the inlet of motor 4.

Since pressure HPI is constant by virtue of valve 7, the pressure HP2 controlling the striker unit 1 varies automatically as a reverse function of the resistant torque, the torque C of motor 4 being proportional to HPl HP2.

Thus, if thresistant torque C increases, HPl HP2 will also increase; but since HPl remains constant due to the presence of regulating valve 7, HP2 is reduced. The force of striker 1 decreases accordingly as the resistant torque counteracting the motor 4 increases.

The embodiment illustrated in FIG. 2 differs from the structure of FIG. I in that the rock drill is supplied through two separate circuits, namely:

a circuit A feeding the motor 4; the supply pressure is HPl and the output O1; and the pressure at the exhaust or outlet of this motor is HP2,

and another circuit B connected to the outlet of motor 4; the pressure in this circuit is HP2, i.e., equal to the exhaust outlet pressure of motor 4, with an output Q2.

The motor 4 will thus operate with an output Q1, but the striker unit 1 operates with the sum of said outputs O1 and Q2. The ratio of these outputs Q1 and O2 is immaterial, for example 50 percent and 50 percent.

The modified form of embodiment illustrated in FIG. 2 further differs from the structure shown in FIG. 1 in that the pressure regulator 7 of FIG. 1 is dispensed with and replaced by a pressure summing valve 8 inserted in circuits A and B upstream of motor 4 and striker unit 1. The function of this valve is to keep at a constant value the sum of pressures I-IPl and I-IPIZ, so that any increment of I-lPl is attended automatically by a reduction of HPZ. Also in this case the force of striker unit 1 decreases when the resistant torque acting on motor 4 increases.

Independently of this essentially advantageous feature constituting the primary object of this invention, the arrangement according to this invention is attended by a complementary advantages, inter alia:

a single and same source of power is used for supplying the motor 4 and striker unit 1,

the number of generally flexible hoses connecting the rock drill to the power generator is extremely reduced, since it comprises only two hoses in the structure of FIG. 1 and three in the structure of FIG. 2,

the influence exerted by frequent and sudden variations in the resistant torque on the motor input pressure is extremely moderate and the useful life of the flexible hoses is thus greatly improved.

Although the present invention has been described with reference to specific embodiments, it will readily occur to those conversant with the art that many modifications and variations may be brought thereto without departing from the scope of the invention as set forth in the appended claims.

Furthermore, it would not constitute a departure from the basic principle of the invention to incorporate same in other types of rock drills, whatever the various names they can be given by professionals or the materials they drill in, as long as they drill thanks to a combination of successive blows on a tool which rotates continuously or step by step after each blow.

What I claim as new is:

l. A rock drill comprising:

a tool holder;

a first hydraulic motor operatively connected to said tool holder for rotating same;

a second hydraulic motor operatively connected to said tool holder for imparting axial impacts thereto, said motors together forming a driver system for said tool holder, each of said hydraulic motors having an inlet and an outlet for hydraulic fluid traversing same;

a first conduit connecting the inlet of said first hydraulic motor to a source of liquid under pressure;

a second conduit connecting the outlet of said first hydraulic motors only to the intake of the second hydraulic motor;

a third conduit leading liquid from the outlet of said second hydraulic motors, said conduits passing liquid through said motors in series circuit whereby an increasing resistance to rotation of said tool holder by said first motor is reflected in a decreased impact force of said second motor upon said tool holder; and

a pressure regulator valve connected between said first conduit and a reservoir to maintain substantially constant the liquid pressure applied to at least part of said driver system; and, said pressure regulator valve draining one of said conduits directly to said reservoir upon the development of excess pressure in said first conduit.

2. A rock drill comprising:

a tool holder;

a first hydraulic motor operatively connected to said tool holder for rotating same;

a second hydraulic motor operatively connected to said tool holder for imparting axial impacts thereto, said motors together forming a driver system for said tool holder, each of said hydraulic motors having an inlet and an outlet for hydraulic fluid traversing same;

a first conduit connecting the inlet of said first hydraulic motor to a source of liquid under pressure;

a second conduit connecting the outlet of said first hydraulic motor only to the intake of the second hydraulic motor;

a third conduit leading liquid from the outlet of said second hydraulic motor, said conduits passing liquid through said motor in a series circuit whereby an increasing resistance to rotation of said tool holder by said first motor is reflected in a decreased impact force of said second motor upon said tool holder; and

a pressure regulator connected to said first conduit to maintain substantially constant the liquid pressure applied to at least part of said driver system;

said pressure regulator being a pressure relief valve connected to said first conduit.

3. A rock drill comprising:

a tool holder;

a first hydraulic motor operatively connected to said tool holder for rotating same;

a second hydraulic motor operatively connected to said tool holder for imparting axial impacts thereto, said motors together forming a driver system for said tool holder, each of said hydraulic motors having an inlet and an outlet for hydraulic fluid traversing same;

a first conduit connecting the inlet of said first motor to a source of liquid under pressure;

a second conduit connecting the outlet of said first hydraulic motor only to the intake of the second hydraulic motor;

a third conduit leading liquid from the outlet of said second hydraulic motor, said conduits passing liquid through said motors in a series circuit whereby an increasing resistance to rotation of said tool holder by said first motor is reflected in a decreased impact force of said second :motor upon said tool holder;

a pressure regulator connected to said first conduit to maintain substantially constant the liquid pressure applied to at least part of said driver system; and

a fourth conduit connecting another source of liquid under pressure to the inlet of said second hydraulic motor, said pressure regulator comprising a pres sure-adding buffer valve connected across said first and fourth conduits. 

1. A rock drill comprising: a tool holder; a first hydraulic motor operatively connected to said tool holder for rotating same; a second hydraulic motor operatively connected to said tool holder for imparting axial impacts thereto, said motors together forming a driver system for said tool holder, each of said hydraulic motors having an inlet and an outlet for hydraulic fluid traversing same; a first conduit connecting the inlet of said first hydraulic motor to a source of liquid under pressure; a second conduit connecting the outlet of said first hydraulic motors only to the intake of the second hydraulic motor; a third conduit leading liquid from the outlet of said second hydraulic motors, said conduits passing liquid through said motors in series circuit whereby an increasing resistance to rotation of said tool holder by said first motor is reflected in a decreased impact force of said second motor upon said tool holder; and a pressure regulator valve connected between said first conduit and a reservoir to maintain substantially constant the liquid pressure applied to at least part of said driver system; and, said pressure regulator valve draining one of said conduits directly to said reservoir upon the development of excess pressure in said first conduit.
 2. A rock drill comprising: a tool holder; a first hydraulic motor operatively connected to said tool holder for rotating same; a second hydraulic motor operatively connected to said tool holder for imparting axial impacts thereto, said motors together forming a driver system for said tool holder, each of said hydraulic motors having an inlet and an outlet for hydraulic fluid traversing same; a first conduit connecting the inlet of said first hydraulic motor to a source of liquid under pressure; a second conduit connecting the outlet of said first hydraulic motor only to the intake of the second hydraulic motor; a third conduit leading liquid from the outlet of said second hydraulic motor, said conduits passing liquid through said motor in a series circuit whereby an increasing resistance to rotation of said tool holder by said first motor is reflected in a decreased impact force of said second motor upon said tool holder; and a pressure regulator connected to said first conduit to maintain substantially constant the liquid pressure applied to at least part of said driver system; said pressure regulator being a pressure relief valve connected to said first conduit.
 3. A rock drill comprising: a tool holder; a first hydraulic motor operatively connected to said tool holder for rotating same; a second hydraulic motor operatively connected to said tool holder for imparting axial impacts thereto, said motors together forming a driver system for said tool holder, each of said hydraulic motors having an inlet and an outlet for hydraulic fluid traversing same; a first conduit connecting the inlet of said first motor to a source of liquid under pressure; a second conduit connecting the outlet of said first hydraulic motor only to the intake of the second hydraulic motor; a third conduit leading liquid from the outlet of said second hydraulic motor, said conduits passing liquid through said motors in a series circuit whereby an increasing resistance to rotation of said tool holder by said first motor is reflected in a decreased impact force of said second motor upon said tool holder; a pressure regulator connected to said first conduit to maintain substantially constant the liquid pressure applied to at least part of said driver system; and a fourth conduit connecting another source of liquid under pressure to the inlet of said second hydraulic motor, said pressure regulator comprising a pressure-adding buffer valve connected across said first and fourth conduits. 